The specific goal of this project is to determine whether normal human chromosomes have the ability to suppress the tumorigenicity of a human lung carcinoma cell line. The technique of microcell transfer was used to introduce the human chromosome 11 (with a translocation to the hypoxanthine guanine phosphoribosyl transferase (HGPRT) region of the X chromosome) of a donor cell line into HGPRT-, ouabain-resistant HuT-292DM mucoepidermoid carcinoma cells. Colonies were isolated which grew in selective medium containing hypoxanthine/aminopterin/thymidine (HAT) and ouabain, and tumorigenicity was assayed by injecting these colonies into nude mice. Most microcell hybrids were suppressed in that there was a decreased probability of tumor formation and the tumors that did arise had an increased latency. The 11/X chromosome was shown by restriction fragment length polymorphism (RFLP) analysis and by karyotype analysis to be present in the colonies injected as well as in the tumors which developed. Thus, the portions of chromosome 11 transferred in these experiments were able to partially suppress the tumorigenic phenotype of HuT-292DM lung carcinoma cells.